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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.eventbus;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import com.google.common.annotations.Beta;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import com.google.common.annotations.VisibleForTesting;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import com.google.common.base.Throwables;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.cache.CacheBuilder;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import com.google.common.cache.CacheLoader;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import com.google.common.cache.LoadingCache;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import com.google.common.collect.HashMultimap;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import com.google.common.collect.Multimap;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import com.google.common.collect.SetMultimap;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import com.google.common.reflect.TypeToken;<a name="line.30"></a>
<span class="sourceLineNo">031</span>import com.google.common.util.concurrent.UncheckedExecutionException;<a name="line.31"></a>
<span class="sourceLineNo">032</span><a name="line.32"></a>
<span class="sourceLineNo">033</span>import java.lang.reflect.InvocationTargetException;<a name="line.33"></a>
<span class="sourceLineNo">034</span>import java.util.Collection;<a name="line.34"></a>
<span class="sourceLineNo">035</span>import java.util.LinkedList;<a name="line.35"></a>
<span class="sourceLineNo">036</span>import java.util.Map.Entry;<a name="line.36"></a>
<span class="sourceLineNo">037</span>import java.util.Queue;<a name="line.37"></a>
<span class="sourceLineNo">038</span>import java.util.Set;<a name="line.38"></a>
<span class="sourceLineNo">039</span>import java.util.concurrent.locks.ReadWriteLock;<a name="line.39"></a>
<span class="sourceLineNo">040</span>import java.util.concurrent.locks.ReentrantReadWriteLock;<a name="line.40"></a>
<span class="sourceLineNo">041</span>import java.util.logging.Level;<a name="line.41"></a>
<span class="sourceLineNo">042</span>import java.util.logging.Logger;<a name="line.42"></a>
<span class="sourceLineNo">043</span><a name="line.43"></a>
<span class="sourceLineNo">044</span>/**<a name="line.44"></a>
<span class="sourceLineNo">045</span> * Dispatches events to listeners, and provides ways for listeners to register<a name="line.45"></a>
<span class="sourceLineNo">046</span> * themselves.<a name="line.46"></a>
<span class="sourceLineNo">047</span> *<a name="line.47"></a>
<span class="sourceLineNo">048</span> * &lt;p&gt;The EventBus allows publish-subscribe-style communication between<a name="line.48"></a>
<span class="sourceLineNo">049</span> * components without requiring the components to explicitly register with one<a name="line.49"></a>
<span class="sourceLineNo">050</span> * another (and thus be aware of each other).  It is designed exclusively to<a name="line.50"></a>
<span class="sourceLineNo">051</span> * replace traditional Java in-process event distribution using explicit<a name="line.51"></a>
<span class="sourceLineNo">052</span> * registration. It is &lt;em&gt;not&lt;/em&gt; a general-purpose publish-subscribe system,<a name="line.52"></a>
<span class="sourceLineNo">053</span> * nor is it intended for interprocess communication.<a name="line.53"></a>
<span class="sourceLineNo">054</span> *<a name="line.54"></a>
<span class="sourceLineNo">055</span> * &lt;h2&gt;Receiving Events&lt;/h2&gt;<a name="line.55"></a>
<span class="sourceLineNo">056</span> * To receive events, an object should:&lt;ol&gt;<a name="line.56"></a>
<span class="sourceLineNo">057</span> * &lt;li&gt;Expose a public method, known as the &lt;i&gt;event handler&lt;/i&gt;, which accepts<a name="line.57"></a>
<span class="sourceLineNo">058</span> *     a single argument of the type of event desired;&lt;/li&gt;<a name="line.58"></a>
<span class="sourceLineNo">059</span> * &lt;li&gt;Mark it with a {@link Subscribe} annotation;&lt;/li&gt;<a name="line.59"></a>
<span class="sourceLineNo">060</span> * &lt;li&gt;Pass itself to an EventBus instance's {@link #register(Object)} method.<a name="line.60"></a>
<span class="sourceLineNo">061</span> *     &lt;/li&gt;<a name="line.61"></a>
<span class="sourceLineNo">062</span> * &lt;/ol&gt;<a name="line.62"></a>
<span class="sourceLineNo">063</span> *<a name="line.63"></a>
<span class="sourceLineNo">064</span> * &lt;h2&gt;Posting Events&lt;/h2&gt;<a name="line.64"></a>
<span class="sourceLineNo">065</span> * To post an event, simply provide the event object to the<a name="line.65"></a>
<span class="sourceLineNo">066</span> * {@link #post(Object)} method.  The EventBus instance will determine the type<a name="line.66"></a>
<span class="sourceLineNo">067</span> * of event and route it to all registered listeners.<a name="line.67"></a>
<span class="sourceLineNo">068</span> *<a name="line.68"></a>
<span class="sourceLineNo">069</span> * &lt;p&gt;Events are routed based on their type &amp;mdash; an event will be delivered<a name="line.69"></a>
<span class="sourceLineNo">070</span> * to any handler for any type to which the event is &lt;em&gt;assignable.&lt;/em&gt;  This<a name="line.70"></a>
<span class="sourceLineNo">071</span> * includes implemented interfaces, all superclasses, and all interfaces<a name="line.71"></a>
<span class="sourceLineNo">072</span> * implemented by superclasses.<a name="line.72"></a>
<span class="sourceLineNo">073</span> *<a name="line.73"></a>
<span class="sourceLineNo">074</span> * &lt;p&gt;When {@code post} is called, all registered handlers for an event are run<a name="line.74"></a>
<span class="sourceLineNo">075</span> * in sequence, so handlers should be reasonably quick.  If an event may trigger<a name="line.75"></a>
<span class="sourceLineNo">076</span> * an extended process (such as a database load), spawn a thread or queue it for<a name="line.76"></a>
<span class="sourceLineNo">077</span> * later.  (For a convenient way to do this, use an {@link AsyncEventBus}.)<a name="line.77"></a>
<span class="sourceLineNo">078</span> *<a name="line.78"></a>
<span class="sourceLineNo">079</span> * &lt;h2&gt;Handler Methods&lt;/h2&gt;<a name="line.79"></a>
<span class="sourceLineNo">080</span> * Event handler methods must accept only one argument: the event.<a name="line.80"></a>
<span class="sourceLineNo">081</span> *<a name="line.81"></a>
<span class="sourceLineNo">082</span> * &lt;p&gt;Handlers should not, in general, throw.  If they do, the EventBus will<a name="line.82"></a>
<span class="sourceLineNo">083</span> * catch and log the exception.  This is rarely the right solution for error<a name="line.83"></a>
<span class="sourceLineNo">084</span> * handling and should not be relied upon; it is intended solely to help find<a name="line.84"></a>
<span class="sourceLineNo">085</span> * problems during development.<a name="line.85"></a>
<span class="sourceLineNo">086</span> *<a name="line.86"></a>
<span class="sourceLineNo">087</span> * &lt;p&gt;The EventBus guarantees that it will not call a handler method from<a name="line.87"></a>
<span class="sourceLineNo">088</span> * multiple threads simultaneously, unless the method explicitly allows it by<a name="line.88"></a>
<span class="sourceLineNo">089</span> * bearing the {@link AllowConcurrentEvents} annotation.  If this annotation is<a name="line.89"></a>
<span class="sourceLineNo">090</span> * not present, handler methods need not worry about being reentrant, unless<a name="line.90"></a>
<span class="sourceLineNo">091</span> * also called from outside the EventBus.<a name="line.91"></a>
<span class="sourceLineNo">092</span> *<a name="line.92"></a>
<span class="sourceLineNo">093</span> * &lt;h2&gt;Dead Events&lt;/h2&gt;<a name="line.93"></a>
<span class="sourceLineNo">094</span> * If an event is posted, but no registered handlers can accept it, it is<a name="line.94"></a>
<span class="sourceLineNo">095</span> * considered "dead."  To give the system a second chance to handle dead events,<a name="line.95"></a>
<span class="sourceLineNo">096</span> * they are wrapped in an instance of {@link DeadEvent} and reposted.<a name="line.96"></a>
<span class="sourceLineNo">097</span> *<a name="line.97"></a>
<span class="sourceLineNo">098</span> * &lt;p&gt;If a handler for a supertype of all events (such as Object) is registered,<a name="line.98"></a>
<span class="sourceLineNo">099</span> * no event will ever be considered dead, and no DeadEvents will be generated.<a name="line.99"></a>
<span class="sourceLineNo">100</span> * Accordingly, while DeadEvent extends {@link Object}, a handler registered to<a name="line.100"></a>
<span class="sourceLineNo">101</span> * receive any Object will never receive a DeadEvent.<a name="line.101"></a>
<span class="sourceLineNo">102</span> *<a name="line.102"></a>
<span class="sourceLineNo">103</span> * &lt;p&gt;This class is safe for concurrent use.<a name="line.103"></a>
<span class="sourceLineNo">104</span> * <a name="line.104"></a>
<span class="sourceLineNo">105</span> * &lt;p&gt;See the Guava User Guide article on &lt;a href=<a name="line.105"></a>
<span class="sourceLineNo">106</span> * "http://code.google.com/p/guava-libraries/wiki/EventBusExplained"&gt;<a name="line.106"></a>
<span class="sourceLineNo">107</span> * {@code EventBus}&lt;/a&gt;.<a name="line.107"></a>
<span class="sourceLineNo">108</span> *<a name="line.108"></a>
<span class="sourceLineNo">109</span> * @author Cliff Biffle<a name="line.109"></a>
<span class="sourceLineNo">110</span> * @since 10.0<a name="line.110"></a>
<span class="sourceLineNo">111</span> */<a name="line.111"></a>
<span class="sourceLineNo">112</span>@Beta<a name="line.112"></a>
<span class="sourceLineNo">113</span>public class EventBus {<a name="line.113"></a>
<span class="sourceLineNo">114</span><a name="line.114"></a>
<span class="sourceLineNo">115</span>  /**<a name="line.115"></a>
<span class="sourceLineNo">116</span>   * A thread-safe cache for flattenHierarchy(). The Class class is immutable. This cache is shared<a name="line.116"></a>
<span class="sourceLineNo">117</span>   * across all EventBus instances, which greatly improves performance if multiple such instances<a name="line.117"></a>
<span class="sourceLineNo">118</span>   * are created and objects of the same class are posted on all of them.<a name="line.118"></a>
<span class="sourceLineNo">119</span>   */<a name="line.119"></a>
<span class="sourceLineNo">120</span>  private static final LoadingCache&lt;Class&lt;?&gt;, Set&lt;Class&lt;?&gt;&gt;&gt; flattenHierarchyCache =<a name="line.120"></a>
<span class="sourceLineNo">121</span>      CacheBuilder.newBuilder()<a name="line.121"></a>
<span class="sourceLineNo">122</span>          .weakKeys()<a name="line.122"></a>
<span class="sourceLineNo">123</span>          .build(new CacheLoader&lt;Class&lt;?&gt;, Set&lt;Class&lt;?&gt;&gt;&gt;() {<a name="line.123"></a>
<span class="sourceLineNo">124</span>            @SuppressWarnings({"unchecked", "rawtypes"}) // safe cast<a name="line.124"></a>
<span class="sourceLineNo">125</span>            @Override<a name="line.125"></a>
<span class="sourceLineNo">126</span>            public Set&lt;Class&lt;?&gt;&gt; load(Class&lt;?&gt; concreteClass) {<a name="line.126"></a>
<span class="sourceLineNo">127</span>              return (Set) TypeToken.of(concreteClass).getTypes().rawTypes();<a name="line.127"></a>
<span class="sourceLineNo">128</span>            }<a name="line.128"></a>
<span class="sourceLineNo">129</span>          });<a name="line.129"></a>
<span class="sourceLineNo">130</span><a name="line.130"></a>
<span class="sourceLineNo">131</span>  /**<a name="line.131"></a>
<span class="sourceLineNo">132</span>   * All registered event handlers, indexed by event type.<a name="line.132"></a>
<span class="sourceLineNo">133</span>   *<a name="line.133"></a>
<span class="sourceLineNo">134</span>   * &lt;p&gt;This SetMultimap is NOT safe for concurrent use; all access should be<a name="line.134"></a>
<span class="sourceLineNo">135</span>   * made after acquiring a read or write lock via {@link #handlersByTypeLock}.<a name="line.135"></a>
<span class="sourceLineNo">136</span>   */<a name="line.136"></a>
<span class="sourceLineNo">137</span>  private final SetMultimap&lt;Class&lt;?&gt;, EventHandler&gt; handlersByType =<a name="line.137"></a>
<span class="sourceLineNo">138</span>      HashMultimap.create();<a name="line.138"></a>
<span class="sourceLineNo">139</span>  private final ReadWriteLock handlersByTypeLock = new ReentrantReadWriteLock();<a name="line.139"></a>
<span class="sourceLineNo">140</span><a name="line.140"></a>
<span class="sourceLineNo">141</span>  /**<a name="line.141"></a>
<span class="sourceLineNo">142</span>   * Logger for event dispatch failures.  Named by the fully-qualified name of<a name="line.142"></a>
<span class="sourceLineNo">143</span>   * this class, followed by the identifier provided at construction.<a name="line.143"></a>
<span class="sourceLineNo">144</span>   */<a name="line.144"></a>
<span class="sourceLineNo">145</span>  private final Logger logger;<a name="line.145"></a>
<span class="sourceLineNo">146</span><a name="line.146"></a>
<span class="sourceLineNo">147</span>  /**<a name="line.147"></a>
<span class="sourceLineNo">148</span>   * Strategy for finding handler methods in registered objects.  Currently,<a name="line.148"></a>
<span class="sourceLineNo">149</span>   * only the {@link AnnotatedHandlerFinder} is supported, but this is<a name="line.149"></a>
<span class="sourceLineNo">150</span>   * encapsulated for future expansion.<a name="line.150"></a>
<span class="sourceLineNo">151</span>   */<a name="line.151"></a>
<span class="sourceLineNo">152</span>  private final HandlerFindingStrategy finder = new AnnotatedHandlerFinder();<a name="line.152"></a>
<span class="sourceLineNo">153</span><a name="line.153"></a>
<span class="sourceLineNo">154</span>  /** queues of events for the current thread to dispatch */<a name="line.154"></a>
<span class="sourceLineNo">155</span>  private final ThreadLocal&lt;Queue&lt;EventWithHandler&gt;&gt; eventsToDispatch =<a name="line.155"></a>
<span class="sourceLineNo">156</span>      new ThreadLocal&lt;Queue&lt;EventWithHandler&gt;&gt;() {<a name="line.156"></a>
<span class="sourceLineNo">157</span>    @Override protected Queue&lt;EventWithHandler&gt; initialValue() {<a name="line.157"></a>
<span class="sourceLineNo">158</span>      return new LinkedList&lt;EventWithHandler&gt;();<a name="line.158"></a>
<span class="sourceLineNo">159</span>    }<a name="line.159"></a>
<span class="sourceLineNo">160</span>  };<a name="line.160"></a>
<span class="sourceLineNo">161</span><a name="line.161"></a>
<span class="sourceLineNo">162</span>  /** true if the current thread is currently dispatching an event */<a name="line.162"></a>
<span class="sourceLineNo">163</span>  private final ThreadLocal&lt;Boolean&gt; isDispatching =<a name="line.163"></a>
<span class="sourceLineNo">164</span>      new ThreadLocal&lt;Boolean&gt;() {<a name="line.164"></a>
<span class="sourceLineNo">165</span>    @Override protected Boolean initialValue() {<a name="line.165"></a>
<span class="sourceLineNo">166</span>      return false;<a name="line.166"></a>
<span class="sourceLineNo">167</span>    }<a name="line.167"></a>
<span class="sourceLineNo">168</span>  };<a name="line.168"></a>
<span class="sourceLineNo">169</span><a name="line.169"></a>
<span class="sourceLineNo">170</span>  /**<a name="line.170"></a>
<span class="sourceLineNo">171</span>   * Creates a new EventBus named "default".<a name="line.171"></a>
<span class="sourceLineNo">172</span>   */<a name="line.172"></a>
<span class="sourceLineNo">173</span>  public EventBus() {<a name="line.173"></a>
<span class="sourceLineNo">174</span>    this("default");<a name="line.174"></a>
<span class="sourceLineNo">175</span>  }<a name="line.175"></a>
<span class="sourceLineNo">176</span><a name="line.176"></a>
<span class="sourceLineNo">177</span>  /**<a name="line.177"></a>
<span class="sourceLineNo">178</span>   * Creates a new EventBus with the given {@code identifier}.<a name="line.178"></a>
<span class="sourceLineNo">179</span>   *<a name="line.179"></a>
<span class="sourceLineNo">180</span>   * @param identifier  a brief name for this bus, for logging purposes.  Should<a name="line.180"></a>
<span class="sourceLineNo">181</span>   *                    be a valid Java identifier.<a name="line.181"></a>
<span class="sourceLineNo">182</span>   */<a name="line.182"></a>
<span class="sourceLineNo">183</span>  public EventBus(String identifier) {<a name="line.183"></a>
<span class="sourceLineNo">184</span>    logger = Logger.getLogger(EventBus.class.getName() + "." + checkNotNull(identifier));<a name="line.184"></a>
<span class="sourceLineNo">185</span>  }<a name="line.185"></a>
<span class="sourceLineNo">186</span><a name="line.186"></a>
<span class="sourceLineNo">187</span>  /**<a name="line.187"></a>
<span class="sourceLineNo">188</span>   * Registers all handler methods on {@code object} to receive events.<a name="line.188"></a>
<span class="sourceLineNo">189</span>   * Handler methods are selected and classified using this EventBus's<a name="line.189"></a>
<span class="sourceLineNo">190</span>   * {@link HandlerFindingStrategy}; the default strategy is the<a name="line.190"></a>
<span class="sourceLineNo">191</span>   * {@link AnnotatedHandlerFinder}.<a name="line.191"></a>
<span class="sourceLineNo">192</span>   *<a name="line.192"></a>
<span class="sourceLineNo">193</span>   * @param object  object whose handler methods should be registered.<a name="line.193"></a>
<span class="sourceLineNo">194</span>   */<a name="line.194"></a>
<span class="sourceLineNo">195</span>  public void register(Object object) {<a name="line.195"></a>
<span class="sourceLineNo">196</span>    Multimap&lt;Class&lt;?&gt;, EventHandler&gt; methodsInListener =<a name="line.196"></a>
<span class="sourceLineNo">197</span>        finder.findAllHandlers(object);<a name="line.197"></a>
<span class="sourceLineNo">198</span>    handlersByTypeLock.writeLock().lock();<a name="line.198"></a>
<span class="sourceLineNo">199</span>    try {<a name="line.199"></a>
<span class="sourceLineNo">200</span>      handlersByType.putAll(methodsInListener);<a name="line.200"></a>
<span class="sourceLineNo">201</span>    } finally {<a name="line.201"></a>
<span class="sourceLineNo">202</span>      handlersByTypeLock.writeLock().unlock();<a name="line.202"></a>
<span class="sourceLineNo">203</span>    }<a name="line.203"></a>
<span class="sourceLineNo">204</span>  }<a name="line.204"></a>
<span class="sourceLineNo">205</span><a name="line.205"></a>
<span class="sourceLineNo">206</span>  /**<a name="line.206"></a>
<span class="sourceLineNo">207</span>   * Unregisters all handler methods on a registered {@code object}.<a name="line.207"></a>
<span class="sourceLineNo">208</span>   *<a name="line.208"></a>
<span class="sourceLineNo">209</span>   * @param object  object whose handler methods should be unregistered.<a name="line.209"></a>
<span class="sourceLineNo">210</span>   * @throws IllegalArgumentException if the object was not previously registered.<a name="line.210"></a>
<span class="sourceLineNo">211</span>   */<a name="line.211"></a>
<span class="sourceLineNo">212</span>  public void unregister(Object object) {<a name="line.212"></a>
<span class="sourceLineNo">213</span>    Multimap&lt;Class&lt;?&gt;, EventHandler&gt; methodsInListener = finder.findAllHandlers(object);<a name="line.213"></a>
<span class="sourceLineNo">214</span>    for (Entry&lt;Class&lt;?&gt;, Collection&lt;EventHandler&gt;&gt; entry : methodsInListener.asMap().entrySet()) {<a name="line.214"></a>
<span class="sourceLineNo">215</span>      Class&lt;?&gt; eventType = entry.getKey();<a name="line.215"></a>
<span class="sourceLineNo">216</span>      Collection&lt;EventHandler&gt; eventMethodsInListener = entry.getValue();<a name="line.216"></a>
<span class="sourceLineNo">217</span><a name="line.217"></a>
<span class="sourceLineNo">218</span>      handlersByTypeLock.writeLock().lock();<a name="line.218"></a>
<span class="sourceLineNo">219</span>      try {<a name="line.219"></a>
<span class="sourceLineNo">220</span>        Set&lt;EventHandler&gt; currentHandlers = handlersByType.get(eventType);<a name="line.220"></a>
<span class="sourceLineNo">221</span>        if (!currentHandlers.containsAll(eventMethodsInListener)) {<a name="line.221"></a>
<span class="sourceLineNo">222</span>          throw new IllegalArgumentException(<a name="line.222"></a>
<span class="sourceLineNo">223</span>              "missing event handler for an annotated method. Is " + object + " registered?");<a name="line.223"></a>
<span class="sourceLineNo">224</span>        }<a name="line.224"></a>
<span class="sourceLineNo">225</span>        currentHandlers.removeAll(eventMethodsInListener);<a name="line.225"></a>
<span class="sourceLineNo">226</span>      } finally {<a name="line.226"></a>
<span class="sourceLineNo">227</span>        handlersByTypeLock.writeLock().unlock();<a name="line.227"></a>
<span class="sourceLineNo">228</span>      }<a name="line.228"></a>
<span class="sourceLineNo">229</span>    }<a name="line.229"></a>
<span class="sourceLineNo">230</span>  }<a name="line.230"></a>
<span class="sourceLineNo">231</span><a name="line.231"></a>
<span class="sourceLineNo">232</span>  /**<a name="line.232"></a>
<span class="sourceLineNo">233</span>   * Posts an event to all registered handlers.  This method will return<a name="line.233"></a>
<span class="sourceLineNo">234</span>   * successfully after the event has been posted to all handlers, and<a name="line.234"></a>
<span class="sourceLineNo">235</span>   * regardless of any exceptions thrown by handlers.<a name="line.235"></a>
<span class="sourceLineNo">236</span>   *<a name="line.236"></a>
<span class="sourceLineNo">237</span>   * &lt;p&gt;If no handlers have been subscribed for {@code event}'s class, and<a name="line.237"></a>
<span class="sourceLineNo">238</span>   * {@code event} is not already a {@link DeadEvent}, it will be wrapped in a<a name="line.238"></a>
<span class="sourceLineNo">239</span>   * DeadEvent and reposted.<a name="line.239"></a>
<span class="sourceLineNo">240</span>   *<a name="line.240"></a>
<span class="sourceLineNo">241</span>   * @param event  event to post.<a name="line.241"></a>
<span class="sourceLineNo">242</span>   */<a name="line.242"></a>
<span class="sourceLineNo">243</span>  public void post(Object event) {<a name="line.243"></a>
<span class="sourceLineNo">244</span>    Set&lt;Class&lt;?&gt;&gt; dispatchTypes = flattenHierarchy(event.getClass());<a name="line.244"></a>
<span class="sourceLineNo">245</span><a name="line.245"></a>
<span class="sourceLineNo">246</span>    boolean dispatched = false;<a name="line.246"></a>
<span class="sourceLineNo">247</span>    for (Class&lt;?&gt; eventType : dispatchTypes) {<a name="line.247"></a>
<span class="sourceLineNo">248</span>      handlersByTypeLock.readLock().lock();<a name="line.248"></a>
<span class="sourceLineNo">249</span>      try {<a name="line.249"></a>
<span class="sourceLineNo">250</span>        Set&lt;EventHandler&gt; wrappers = handlersByType.get(eventType);<a name="line.250"></a>
<span class="sourceLineNo">251</span><a name="line.251"></a>
<span class="sourceLineNo">252</span>        if (!wrappers.isEmpty()) {<a name="line.252"></a>
<span class="sourceLineNo">253</span>          dispatched = true;<a name="line.253"></a>
<span class="sourceLineNo">254</span>          for (EventHandler wrapper : wrappers) {<a name="line.254"></a>
<span class="sourceLineNo">255</span>            enqueueEvent(event, wrapper);<a name="line.255"></a>
<span class="sourceLineNo">256</span>          }<a name="line.256"></a>
<span class="sourceLineNo">257</span>        }<a name="line.257"></a>
<span class="sourceLineNo">258</span>      } finally {<a name="line.258"></a>
<span class="sourceLineNo">259</span>        handlersByTypeLock.readLock().unlock();<a name="line.259"></a>
<span class="sourceLineNo">260</span>      }<a name="line.260"></a>
<span class="sourceLineNo">261</span>    }<a name="line.261"></a>
<span class="sourceLineNo">262</span><a name="line.262"></a>
<span class="sourceLineNo">263</span>    if (!dispatched &amp;&amp; !(event instanceof DeadEvent)) {<a name="line.263"></a>
<span class="sourceLineNo">264</span>      post(new DeadEvent(this, event));<a name="line.264"></a>
<span class="sourceLineNo">265</span>    }<a name="line.265"></a>
<span class="sourceLineNo">266</span><a name="line.266"></a>
<span class="sourceLineNo">267</span>    dispatchQueuedEvents();<a name="line.267"></a>
<span class="sourceLineNo">268</span>  }<a name="line.268"></a>
<span class="sourceLineNo">269</span><a name="line.269"></a>
<span class="sourceLineNo">270</span>  /**<a name="line.270"></a>
<span class="sourceLineNo">271</span>   * Queue the {@code event} for dispatch during<a name="line.271"></a>
<span class="sourceLineNo">272</span>   * {@link #dispatchQueuedEvents()}. Events are queued in-order of occurrence<a name="line.272"></a>
<span class="sourceLineNo">273</span>   * so they can be dispatched in the same order.<a name="line.273"></a>
<span class="sourceLineNo">274</span>   */<a name="line.274"></a>
<span class="sourceLineNo">275</span>  void enqueueEvent(Object event, EventHandler handler) {<a name="line.275"></a>
<span class="sourceLineNo">276</span>    eventsToDispatch.get().offer(new EventWithHandler(event, handler));<a name="line.276"></a>
<span class="sourceLineNo">277</span>  }<a name="line.277"></a>
<span class="sourceLineNo">278</span><a name="line.278"></a>
<span class="sourceLineNo">279</span>  /**<a name="line.279"></a>
<span class="sourceLineNo">280</span>   * Drain the queue of events to be dispatched. As the queue is being drained,<a name="line.280"></a>
<span class="sourceLineNo">281</span>   * new events may be posted to the end of the queue.<a name="line.281"></a>
<span class="sourceLineNo">282</span>   */<a name="line.282"></a>
<span class="sourceLineNo">283</span>  void dispatchQueuedEvents() {<a name="line.283"></a>
<span class="sourceLineNo">284</span>    // don't dispatch if we're already dispatching, that would allow reentrancy<a name="line.284"></a>
<span class="sourceLineNo">285</span>    // and out-of-order events. Instead, leave the events to be dispatched<a name="line.285"></a>
<span class="sourceLineNo">286</span>    // after the in-progress dispatch is complete.<a name="line.286"></a>
<span class="sourceLineNo">287</span>    if (isDispatching.get()) {<a name="line.287"></a>
<span class="sourceLineNo">288</span>      return;<a name="line.288"></a>
<span class="sourceLineNo">289</span>    }<a name="line.289"></a>
<span class="sourceLineNo">290</span><a name="line.290"></a>
<span class="sourceLineNo">291</span>    isDispatching.set(true);<a name="line.291"></a>
<span class="sourceLineNo">292</span>    try {<a name="line.292"></a>
<span class="sourceLineNo">293</span>      Queue&lt;EventWithHandler&gt; events = eventsToDispatch.get();<a name="line.293"></a>
<span class="sourceLineNo">294</span>      EventWithHandler eventWithHandler;<a name="line.294"></a>
<span class="sourceLineNo">295</span>      while ((eventWithHandler = events.poll()) != null) {<a name="line.295"></a>
<span class="sourceLineNo">296</span>        dispatch(eventWithHandler.event, eventWithHandler.handler);<a name="line.296"></a>
<span class="sourceLineNo">297</span>      }<a name="line.297"></a>
<span class="sourceLineNo">298</span>    } finally {<a name="line.298"></a>
<span class="sourceLineNo">299</span>      isDispatching.remove();<a name="line.299"></a>
<span class="sourceLineNo">300</span>    }<a name="line.300"></a>
<span class="sourceLineNo">301</span>  }<a name="line.301"></a>
<span class="sourceLineNo">302</span><a name="line.302"></a>
<span class="sourceLineNo">303</span>  /**<a name="line.303"></a>
<span class="sourceLineNo">304</span>   * Dispatches {@code event} to the handler in {@code wrapper}.  This method<a name="line.304"></a>
<span class="sourceLineNo">305</span>   * is an appropriate override point for subclasses that wish to make<a name="line.305"></a>
<span class="sourceLineNo">306</span>   * event delivery asynchronous.<a name="line.306"></a>
<span class="sourceLineNo">307</span>   *<a name="line.307"></a>
<span class="sourceLineNo">308</span>   * @param event  event to dispatch.<a name="line.308"></a>
<span class="sourceLineNo">309</span>   * @param wrapper  wrapper that will call the handler.<a name="line.309"></a>
<span class="sourceLineNo">310</span>   */<a name="line.310"></a>
<span class="sourceLineNo">311</span>  void dispatch(Object event, EventHandler wrapper) {<a name="line.311"></a>
<span class="sourceLineNo">312</span>    try {<a name="line.312"></a>
<span class="sourceLineNo">313</span>      wrapper.handleEvent(event);<a name="line.313"></a>
<span class="sourceLineNo">314</span>    } catch (InvocationTargetException e) {<a name="line.314"></a>
<span class="sourceLineNo">315</span>      logger.log(Level.SEVERE,<a name="line.315"></a>
<span class="sourceLineNo">316</span>          "Could not dispatch event: " + event + " to handler " + wrapper, e);<a name="line.316"></a>
<span class="sourceLineNo">317</span>    }<a name="line.317"></a>
<span class="sourceLineNo">318</span>  }<a name="line.318"></a>
<span class="sourceLineNo">319</span><a name="line.319"></a>
<span class="sourceLineNo">320</span>  /**<a name="line.320"></a>
<span class="sourceLineNo">321</span>   * Flattens a class's type hierarchy into a set of Class objects.  The set<a name="line.321"></a>
<span class="sourceLineNo">322</span>   * will include all superclasses (transitively), and all interfaces<a name="line.322"></a>
<span class="sourceLineNo">323</span>   * implemented by these superclasses.<a name="line.323"></a>
<span class="sourceLineNo">324</span>   *<a name="line.324"></a>
<span class="sourceLineNo">325</span>   * @param concreteClass  class whose type hierarchy will be retrieved.<a name="line.325"></a>
<span class="sourceLineNo">326</span>   * @return {@code clazz}'s complete type hierarchy, flattened and uniqued.<a name="line.326"></a>
<span class="sourceLineNo">327</span>   */<a name="line.327"></a>
<span class="sourceLineNo">328</span>  @VisibleForTesting<a name="line.328"></a>
<span class="sourceLineNo">329</span>  Set&lt;Class&lt;?&gt;&gt; flattenHierarchy(Class&lt;?&gt; concreteClass) {<a name="line.329"></a>
<span class="sourceLineNo">330</span>    try {<a name="line.330"></a>
<span class="sourceLineNo">331</span>      return flattenHierarchyCache.getUnchecked(concreteClass);<a name="line.331"></a>
<span class="sourceLineNo">332</span>    } catch (UncheckedExecutionException e) {<a name="line.332"></a>
<span class="sourceLineNo">333</span>      throw Throwables.propagate(e.getCause());<a name="line.333"></a>
<span class="sourceLineNo">334</span>    }<a name="line.334"></a>
<span class="sourceLineNo">335</span>  }<a name="line.335"></a>
<span class="sourceLineNo">336</span><a name="line.336"></a>
<span class="sourceLineNo">337</span>  /** simple struct representing an event and it's handler */<a name="line.337"></a>
<span class="sourceLineNo">338</span>  static class EventWithHandler {<a name="line.338"></a>
<span class="sourceLineNo">339</span>    final Object event;<a name="line.339"></a>
<span class="sourceLineNo">340</span>    final EventHandler handler;<a name="line.340"></a>
<span class="sourceLineNo">341</span>    public EventWithHandler(Object event, EventHandler handler) {<a name="line.341"></a>
<span class="sourceLineNo">342</span>      this.event = checkNotNull(event);<a name="line.342"></a>
<span class="sourceLineNo">343</span>      this.handler = checkNotNull(handler);<a name="line.343"></a>
<span class="sourceLineNo">344</span>    }<a name="line.344"></a>
<span class="sourceLineNo">345</span>  }<a name="line.345"></a>
<span class="sourceLineNo">346</span>}<a name="line.346"></a>




























































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